A typical telescopic sight for use with a firearm includes a reticle having centrally located cross hairs, for example a vertical centerline and a horizontal centerline. Commonly, telescopic sights include adjustment controls that enable the operator of the firearm to make several main adjustments to the telescopic sight relative to the firearm. Three of these adjustments are an elevation adjustment of the horizontal hairline (i.e., movement of the horizontal hairline up or down), a lateral adjustment of the vertical hairline (i.e., movement of the vertical hairline left or right), and a rotational adjustment of the entire telescopic sight about the central axis of the telescopic sight.
The elevation adjustment is used to compensate for the arched path a fired projectile (e.g., bullet) will inherently follow from the muzzle of the firearm to the target. Once the elevation of a sight is properly adjusted for a given range, the intersection of the cross-hairs of the reticle will indicate a theoretical point of impact of the bullet at that range, even though the line of fire to the target (e.g., the actual path of the bullet), will not align with the line of sight (i.e., the straight line extension of the central axis of the telescopic sight to the target).
The lateral adjustment is used primarily for initial sighting, and also to compensate for any expected drift (e.g., left or right drift) by the bullet from the line of fire caused by cross winds between the firearm and the target.
The process of making elevation and windage adjustments to the sight of a firearm is called “sighting in.” These adjustments typically will not remain consistent between sessions (or in some circumstances, even between successive shots), and are often difficult to adjust accurately prior to test-firing the firearm.
Apart from collimating the sight with the firearm, the mounted telescopic sight is rotatable about its central axis to adjust the relative position of the cross hairs of the sight with respect to the longitudinal and vertical axis of the barrel of the firearm (i.e., the bore axis). The adjustment is made to ensure that the vertical cross hair of the sight coincides with the vertical axis of the firearm. This adjustment can be made using a padded vice or cradle, a machinist's level, and a known vertical reference line. However, in the field, this adjustment has been proven to be quite difficult to execute accurately due to the lack of a known vertical reference line with respect to the bore axis of the barrel of the firearm.
One common method used to attempt to align the vertical cross hair of the sight with respect to the bore axis of the firearm includes holding the firearm perfectly level with respect to the ground and then “sighting in” on a reference line, such as the edge of a building which is known vertical with respect to the ground. With this method, the telescopic sight is simply rotated until the reference line and the vertical cross hair align. Unfortunately, however, this method is rarely successful because without the previously mentioned machinist's level and padded vise, there is no indication of when the firearm is being held truly level with respect to the ground. Since it is common to hold a firearm, such as a rifle, at a slight tilt or cant, any adjustment to the reticle will reflect the angle of the cant and will invariably fail to be truly aligned with the bore axis of the barrel of the firearm.
The problem with aligning the vertical hairline with respect to the bore axis of the firearm is that there is no fixed reference line against which such an adjustment may be accurately and easily made. Conventional mounts for mounting a sight to a firearm do not restrict or otherwise provide “self-alignment” of the mounted sight with respect to the bore axis of the firearm. Any reference line located on the sight will not remain (or may never be) consistently aligned with respect to the bore axis of the firearm, and therefore may not be used to properly adjust the hairlines of the reticle with respect to the bore axis of the firearm.
What is needed is an easy-to-use reticle alignment device for quickly aligning the cross-hairs of the reticle of a firearm-mounted telescopic sight with respect to the bore axis of the firearm. The device should include one or more apparatuses for quickly and accurately mounting the device on the firearm.